Heavy crude oil contains a substantial proportion of asphaltenes and other hydrocarbons which are associated with large amounts of sulfur, nitrogen and metals. In past times, these heavy fractions were usually found to be applicable in paving materials and converted to valuable product using thermal processes. Today, due to the cost and enormous demands for petroleum, these fractions require processing to form more valuable products, which are relatively low in sulfur and lower boiling hydrocarbons that can be used as clean fuels. It is known in the art that this reduction in metal, sulfur and conversion to lower boiling hydrocarbons can be carried out with hydrogen and a solid catalyst at elevated temperatures and pressure. Prior catalysts are very different from the catalyst of the present invention.
WO 0,253,286 claims a hydroprocessing catalyst for the conversion of the heavy oil hydrocarbons, which contains a transition metal of group VI in a concentration of 7 to 20 weight % and a metal of group VIII in a concentration of 0.5-6 weight % in a calcined catalyst, which correspond to oxide composition over a support of alumina. Also claimed is a process for the hydroprocessing of heavy hydrocarbon feedstock with the catalyst of the invention in fixed or ebullated bed.
U.S. Pat. No. 4,225,421 discloses a process for hydrodemetallation and hydrodesulfurization of hydrocarbon feedstocks containing asphaltenes and metals by contacting the feedstock with hydrogen and a bimodal catalyst consisting essentially of a Group VIB hydrogenation metal on a support comprising alumina wherein said catalyst has a surface area of about 140-300 m2/g and a total pore volume of about 0.4-1.0 cc/g. Out of that total pore volume, 0.06-0.3 cc/g can be pores having a radius greater than 60 nm. U.S. Pat. No. 4,746,419 discloses a bimodal catalyst characterized by a surface area of 75-400 m2/g and a total pore volume of 0.5-1.5 cc/g. Out of that total pore volume, 0.2-0.3 cc/g are in pores greater than 60 nm radius and not more than 0.15 cc/g in pores greater than 200 nm radius. U.S. Pat. Nos. 4,225,421 and 4,746,419 disclose that high surface area, bimodal catalysts are desirable for hydroprocessing heavy hydrocarbon feedstocks. These patents fail to disclose an understanding that the manner in which the pore volume is distributed throughout the range of pores that are less than 60 nm radius can make a difference in catalyst performance.
U.S. Pat. No. 5,545,602 claims a catalyst with a composition containing very high amount of group VIII and group VIB metals along with phosphorus oxide, with a surface area of 150-240 m2/g, total pore volume of 0.7-0.98 cm3/g, and a pore volume distribution where less than 20% corresponds to the micro-pore zone with diameter of 10 nm, about 34-74% corresponds to pores within a 10-20 nm interval, from 26-46% corresponds to the region of meso-pores with pore diameter of 20 nm, 22-32% with pore diameters of 25 nm, and the macro-pore region with diameters of 100 nm contributes with 14-22%. This patent mainly claims the process for residua feedstock having 4-6° API gravity.
U.S. Pat. No. 6,218,333 discloses a detailed method for the preparation of a catalyst by means of a porous support (alumina, silica-alumina, silica, titanium, boron, zeolites, zirconium, magnesium and their combinations) with one or more active metals (Mo, W, Co, Ni and their oxides, sulfides and mixtures of them). The object of this patent is to find out the proper method of activation before catalytic activities.
U.S. Pat. No. 4,687,757 claims an alumina support which can contain compounds of transition metals titanium and one of molybdenum having a surface area in the 100-250 m2/g interval, while they are neither claiming the interval of pore volume nor the average pore diameter, both of which are very important properties particularly when the hydrotreating feedstock are residues and/or heavy crude oils. In the detailed description of the patent they reveal a volume of pore of 0.2-2.0 cm3/g, which was determined in mercury penetration equipment. From these data it is evident that the catalyst of the referred patent is used mainly in the hydrodemetallization stage, which contains titania in the support.
On the other hand, the present invention balances catalyst textural properties to provide a catalyst that admits a maximum amount of treatable hydrocarbons into the pores of the catalyst, while at the same time providing access to a maximum number of active catalytic sites on the surface as well as inside the pores without diffusion limitations.
In addition, the present invention involves a catalyst providing higher conversion of heavy hydrocarbon feedstocks along with sufficient stability with time on stream. Thus, the present catalyst is economically attractive since it maximizes the balance of catalyst life and activity of hydroprocessing. The present catalyst is provided by variation of the support composition (different alumina) or different pore diameter of the catalyst.
The above representative patents disclose catalyst formulations and other useful catalyst components along with their process conditions. All of them are with alumina catalysts.